1. Field of the Invention
This invention pertains generally to a zero insertion force ("ZIF") socket and, more particularly, a ZIF socket adapted for use in high density circuits.
2. Background Information
Integrated circuits are typically encapsulated in a plastic shell through which electrical couplings are made with one or more pins. The integrated circuit, shell, and pins typically constitute a discrete electronic component referred to as an integrated circuit package. Frequently, integrated circuit packages are inserted into a socket mounted to a printed circuit ("PC") board. The pins of the integrated circuit package are inserted into corresponding holes of the socket, whereupon they contact the terminals of the socket. Electrical couplings can be made to the pins of the integrated circuit package in any number of ways known to the art.
Historically, integrated circuit packages were dropped directly into a socket and then secured by applying pressure to the top of the package to force the contact with the socket terminals. This type of socket came to be known as a "low insertion force" ("LIF") socket. This technique frequently yielded bent or broken pins when pins were misaligned with the socket's holes, and packages with bent or broken pins were typically discarded. Early integrated circuit packages were relatively inexpensive, and so economic losses from these errors were tolerable. However, as integrated circuits became larger, more powerful, and more expensive, such losses became less acceptable. Thus, alternative techniques were developed.
One technique developed in response to this concern was the zero insertion force ("ZIF") socket. A ZIF socket typically is an assembly of a top and a bottom with a cammed lever extending from one side. The top and bottom define a plurality of relatively large holes with which the pins are aligned as the package is inserted. However, instead of applying pressure to the top of the package to contact the pins with the terminals, the cammed lever is flipped to move the top laterally relative to the bottom to create the electrical coupling.
ZIF sockets are generally used to couple processors to circuits fabricated on printed circuit boards. Processors such as microprocessors and digital signal processors are expensive and have relatively large numbers of pins. Thus, the advantages of using ZIF sockets rather than LIF sockets are particularly important as to processors.
One significant drawback to using traditional ZIF socket designs is the large amount of space they occupy. ZIF sockets are typically mounted to PC boards by inserting mounting pins through holes in the board whereupon couplings are soldered to the opposite side of the board. Thus, a single integrated circuit package requires both sides of the board. Through-board mounting techniques consequently also lengthen bus lines, thereby restricting processor operating speeds. These ZIF socket designs also employ a certain amount of space for operating the lever that must be thrown to establish and break the electrical coupling. Thus, ZIF sockets generally do not allow close placement of boards within a computer. Applications employing electronic components in high density, such as "laptop" or "notebook" computers, consequently use LIF sockets rather than ZIF sockets.
However, traditional ZIF socket designs are becoming problematical for some applications as the demands on personal computing resources rise. More particularly, new personal computers, even desktop versions, require ever higher densities of electrical components operating at still higher speeds. Traditional ZIF socket designs are deficient not only in that they require relatively large amounts of space, but also in that they decrease operating speeds. Thus, there is a need for a new ZIF socket design to address these and other drawbacks.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.